I am using Multisim to make a counter that counts to 1 minute. I am using a binary counter to count to 15 and using jk flip flops to count to 4 (1 for every 15 seconds). I am trying to get the multiplexer in the circuit to output a 1 at 14 so it is realy to register at the flip flops on the next clock cycle. The multiplexer keeps flickering at 12 causing the flip flops to go prematurely. Anyone have any suggestions?

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Why don't you use a logic gate combination to detect the number 14? The choice of the Multiplexer is rather odd. Not that it's wrong, just odd.

Keep in mind that you don't have to make the FF count up exactly at number 15. You just need them to count up at the same number on each 1-to-15 count. Every number of the counter comes with the same frequency.

 

Funny you talk about logic gates. I actually tried the multiplexer after failing to get the desired with results. Guess what, it does the same thing with all of the outputs of the counter anded together. What I did was inverted the A output so it would go on 14. I am guess that the propagation time has to do something with it. When it transitions from 11 to 12, for just a nano second, it shows all of the outputs high I am guessing.

 

Possibly. It's an overkill, but you can detect the number 13 and put a D Flip Flop in order to delay the result for 1 cycle.